MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGB Technical - Fuel and Temp gauges

Any wise ideas and could this be a bi-metal voltage stabliser problem?
1969 MGB GT, recently acquired, and fine overall condition ..but ..
Fuel gauge:
Shows tank level when ignition is first switched on and then fades to either 1/4 or empty.
tried a new new tank flats unit: same problem.
Tried a new gauge: same problem.
Tried shorting the 2 tank connections: same problem.

Temp gauge:
(It's the capillary version)
Never moves from C.
Waiting for spares to arrive from UK before being able to dtermine anything further.

I notice that in the Haynes book electric diagrams that the 2 gauges share the same bi-metal volage stabliser.
Thus the question.





Harp Bamrah

One more thing: Can anyone advise of the most well stocked place for MG "stuff" in London. I am there (at the Intercon Hotel in Mayfair) for a short business trip mid January, and would love to pick up a few bits and pieces. Will not have much spare time...

Thanks, and all the best 2002 ,
Harp
Harp Bamrah

If I didn't know better, I'd say your problem was either with the voltage regulator thingy.. (nice tech-speak eh?) or a bad ground. Its the small brick that the fuel gauge is attached to that is connected that is on the wall behind the dash.

I don't know what they call it, but in essence its a voltage regulator. Sometimes when a device as such gets old, it will give an erratic voltage (or none at all!). The fuel guage requires about 11.8 ish volts(this is from memory, so don't take that number as gospel).

How to diagnose:

Get a voltmeter. Digital is best. Find the side of the regulator thats the "output" If I had a diagram I'd tell you which side of it. In fact, I seem to remember some other bit of electronics borrowing power from the "input" side of it, so ensure you get the correct side.

Now, ensure the car is dead cold. Do NOT do this after the car has been electrically active for any length of time (ie has had the key ON) So, hook up your meter, ensure you have a good solid ground, and then turn on your key, and watch, and note the voltage output. Be very picky about this, cause a drop of only a volt or two can bugger up the whole works. So, make some notes, and see where this leads.

Oh, and check for a good solid ground. The fuel sender unit derives its ground in the trunk if I remember correctly, so, make sure it has a solid solid solid ground.

Cheers
Gord Bestwick

Harp,
From 1968 on the MGs had a VOLTAGE STABILIZER, part # BHA4602 for the Temp and Fuel gauges. If both gauges started acting up at the same time I will bet it is the voltage stabilizer. On my US spec 'B' it is located behind the dash (fascia) near the Tach. It is held in place by one screw. It is a fiddley little thing to replace, but will most likely cure both your Temp and Fuel gauge problems.

Dave
David Kalp

Harp

the best stock dealer in london?...as far as i know the only ones in London you could go to is.....

Moss Motors Hampton Farm Industrial Estate, Hanworth, Middx, TW13 6DB
www.moss-europe.co.uk
Tel: 020 8867 2020 Fax: 020 8867 2030 Freefone: 0800 919971

Just outside London I would suggest....

MGB Hive Marshall's Bank, Parson Drove, Wisbech, Cambs, PE14 7ES Tel: 01945 700500 Fax: 01945 700130
www.mgbhive.co.uk
Not quite in London but they are very helpful

There is a list of parts suppliers on this page

www.mgcars.org.uk/carclub/index.html

good luck


ian holliday

David,Gord,
Thanks very much.
Found an old (may not be any good) thingy, and will have a fiddle tomorrow.
Ian,
Thanks for the comprehensive contacts.
All the best from Singapore where it hasnt stopped raining for 30 hours.
Bad for golf, and bad for fiddling.
Harp
Harp Bamrah

Harp: Go to this site:http://www.mgbexperience.com/electrical/
Click on "instruments" then "stabilizer". Rick has an excellent discussion on the stabilizer. Don't bother with an OE replacement, build one like Rick describes. It's cheap, easy, and will work a whole lot better.
JH

The capillary temp gauge (one half of the dual oil/temp gauge) doesn't use the stabiliser - it is mechanical not electric. It is not 'user serviceable' and is usually an exchange item, in the UK at least.

Your fuel gauge problem could well be the stabiliser - when you first switch on it applies full 12v to the gauge, then a couple of seconds later starts switching the 12v off and on once every second or so. Easy to test, just connect a voltmeter or test-lamp to the light-green/green wire on the stabiliser.
Paul Hunt

harp
I had the same Symptoms as you mention. i changed the voltage regulator and its working fine.
andy

A very good place for ALL MGB spares is Brown & Gammons in Baldock. Although not in London, they can be reached on the direct East Coast Main Line from Kings Cross in about 50 minutes and their workshops and showrooms are about 5 minutes walk from Baldock railway station. Their website is www.ukmgparts.com and their E-mail is sales@ukmgparts.com. Contact Ron or Malcolm Gammons, or Peter Edney for all the expert advice you could wish for.
Have a good stay in the UK

David Robinson
David Robinson

This thread was discussed between 26/12/2001 and 28/12/2001

MG MGB Technical index

This thread is from the archive. The Live MG MGB Technical BBS is active now.